Blower Motor Failure

Symptoms

• No airflow from any vent on any fan speed setting [2].
• Blower works normally when cold but stops functioning on all settings after running the A/C or heater for an extended period [2].
• Intermittent loss of blower operation — fan cuts out while driving and may return later [0].
• Fault code B1007-008 stored, indicating a short to ground in blower circuit A (traced to an internal motor wiring fault) [0].
• Blower motor runs but only at one speed regardless of the switch position — this pattern points toward the resistor rather than the motor itself [2].
• Rapid or repeated blower motor resistor failures, suggesting the motor is drawing excessive current due to worn or dry bearings [5].

Causes

• Internal motor wiring (brush leads) shorting to ground inside the motor housing, confirmed by fault code B1007-008 (short to ground in blower circuit A) [0].
• Motor armature or brushes worn out, resulting in an open circuit inside the motor — confirmed by continuity test [2].
• Aged or dry motor bushings/bearings increasing current draw, which shortens resistor life and eventually burns out the motor [5].
• ATC control module internal relay with bad contacts or poor connection, cutting power to all fan speeds [23].
• Blocked cabin air filter or vent obstruction increasing load on the motor [5].

Diagnosis

• Check voltage at the blower motor wiring harness connector — if 11–12 V is present at the plug but the motor will not run, the motor itself is faulty [2].
• Perform a continuity test on the old motor: no continuity confirms the motor is open-circuit and needs replacement [2].
• If the blower runs only at the highest speed on all switch positions, suspect the resistor block rather than the motor [2].
• If the blower fails on all speeds simultaneously, inspect the ATC control module for a faulty board-mounted relay that feeds all fan speeds [23].
• Read fault codes with a DRBIIIt scan tool — code B1007-008 points to a short to ground in the blower motor circuit, which can originate inside the motor [0].
• With the motor removed from the housing, inspect brush leads and internal wiring for contact with the motor internals (shorting to ground) [0].
• If repeated resistor failures are occurring, remove the motor and inspect/lubricate the shaft; a motor that is stiff or noisy is overloading the resistor [5].

Repair

The front blower motor is secured by only three screws inside the ventilation housing and is accessible after removing the engine air cleaner housing cover — most owners with basic tools can replace it in under an hour [1, 2, 3]. The motor and squirrel-cage fan are sold as one combined unit [2]. The main risk is an accidental airbag deployment if instrument panel work is required, but the blower motor itself does not require instrument panel removal [1, 3]. Forum consensus is to buy an OEM replacement unit rather than attempting brush or bearing repairs on the sealed motor [0, 5].

Parts

Plain part names — affiliate links and pricing are coming in a later update.

• Blower motor assembly with squirrel-cage fan (motor and fan are sold as one combined unit — order the blower assembly) [2]

Related forum threads

• 19 ↳Ok wits end time
• 19 ↳Blower motor resistor repair??
• 19 ↳Blower motor resistor problems
• 19 ↳Heat/ A/C fan quit while on a road trip, suspect worn out brushes,.... is there a temp fix?

From the manuals

• Workshop manual (2004–2006)

  "(2) Remove the engine air cleaner housing cover (Refer to 9 - ENGINE/AIR INTAKE SYSTEM/AIR CLEANER ELEMENT - REMOVAL). (3) Position the ventilation housing insulation blanket out of the way of the blower motor assembly. (4) Disconnect the wire harness connector from the blower motor (Fig. 4). (5) Remove the three blower motor retaining screws. (6) Remove the blower motor assembly from the ventilation housing. INSTALLATION (1) Install the blower motor assembly into the ventilation housing. (2) Install the three blower motor retaining screws. Tighten the screws to 2 N·m (17 in. lbs.). (3) Connec"

• Workshop manual (2000–2003)

  "(6) If servicing the passenger side air outlets, install the passenger side airbag (Refer to 8 - ELECTRICAL/RESTRAINTS/PASSENGERAIRBAGINSTALLATION). (7) If servicing the driver side air outlets, install the instrument cluster bezel (Refer to 23 - BODY/INSTRUMENT PANEL/CLUSTER BEZEL - INSTALLATION). (8) Reconnect the battery negative cable. BLOWER MOTOR REMOVAL (1) Disconnect and isolate the negative battery cable. (2) Remove the engine air cleaner housing cover (Refer to 9 - ENGINE/AIR INTAKE SYSTEM/AIR CLEANER ELEMENT - REMOVAL). Fig. 2 Passenger Side Air Nozzle Cover 1 - FRONT SCREWS (2) 2 -"

• Workshop manual (2000–2003)

  "The switch is serviced only as a part of the heater-A/C control. DIAGNOSIS AND TESTING - BLOWER MOTOR SWITCH The blower motor switch can be diagnosed by using the DRBIIItscan tool. Refer to Body Diagnostic Procedures. For circuit descriptions and diagrams, refer to the appropriate wiring information. REMOVAL WARNING: ON VEHICLES EQUIPPED WITH AIRBAGS, DISABLE THE AIRBAG SYSTEM BEFORE ATTEMPTING ANY STEERING WHEEL, STEERING COLUMN, OR INSTRUMENT PANEL COMPONENT DIAGNOSIS OR SERVICE. DISCONNECT AND ISOLATE THE BATTERY NEGATIVE (GROUND) CABLE, THEN WAIT TWO MINUTES FOR THE AIRBAG SYSTEM CAPACITOR"

• Workshop manual (2000–2003)

  "The compressor draws in low-pressure refrigerant vapor from the evaporator through its suction port. It then compresses the refrigerant into a high-pressure, high-temperature refrigerant vapor, which is then pumped to the condenser through the compressor discharge port. The compressor cannot be repaired. If faulty or damaged, the entire compressor assembly must be replaced. The compressor clutch, pulley, and coil, are available for service. DIAGNOSIS AND TESTING - COMPRESSOR NOISE When investigating an air conditioning related noise, you must first know the conditions under which the noise occ"

• Mercedes fault-code reference

  "Cable from (terminal 85) ground circuit Kn/4 conditioning auxiliary fan (M45) to ground point W5 has a short circuit to voltage(+) or open circuit. d. Relay for auxiliary fan (K77) is faulty. e. Fuse F119 is faulty. f. Auxiliary fan motor (M45) is faulty or fan has excessive debris preventing it from operating. D The Complete Sprinter Fault Code Guide -HVAC Systems --Automatic Climate Control Daimler Dodge DRB3 Component or variable monitored Fault Sub Fault Sub Code Fault Code Fault (MB Component Number) B100C 015 900C OF Self test failure HZR [ATC] control unit (A81): Heating mode Self-test"

• Workshop manual (2004–2006)

  "(22) Install the cover onto the rear A/C condenser housing (Refer to 24 - HEATING & AIR CONDITIONING/DISTRIBUTION - REAR/A/C CONDENSER COVER - INSTALLATION). AIR FILTER REMOVAL (1) Unlock the eight quick-release fasteners by turning them 90 degrees counter clockwise (Fig. 6). (2) Remove the rear air inlet grate from the rear A/C evaporator cover. (3) Remove the rear particulate air filter by disengaging the velcro-type retainers. (4) Carefully clean the rear particulate air filter using compressed air. INSTALLATION NOTE: Replace the rear particulate air filter if it is heavily soiled or damage"

Sources